Coach John Harbaugh said Monday afternoon that Lewis, who has missed the last five games after tearing his right triceps in the team's 31-29 win against the Dallas Cowboys on Oct. 14, is eligible to be activated from injured reserve-designated to return this week.

Without saying that Lewis would practice Thursday — the first day he is eligible to do so — Harbaugh said the 37-year-old linebacker is on pace to return earlier than anticipated.

"I think he will," Harbaugh said during his weekly news conference at the team's training facility in Owings Mills. "That's a best guess. He's working hard to do that. We'll see."

Getting Lewis back this season was a priority for the Ravens, who elected to avoid shelving him for the entire season.

If Lewis were to return this week, the first game that he would be eligible to play in is the team's home contest against the Denver Broncos on Dec. 16. But Harbaugh said everything depends on timing to make sure Lewis is ready to return this week.

"... We're going to have to test it, to see if it can hold up," Harbaugh said. "Really don't know where it's at right now. Ray has been in rehab mode. So he hasn't been here from a football standpoint in terms of us seeing any of that. But just talking to Ray, it sounds like things have gone well. There have been no setbacks. So there's a possibility."

The Ravens dropped their first game without Lewis, absorbing a 43-13 pounding by the Houston Texans on Oct. 21. Since then, however, the team has strung together four consecutive wins. Coupled with the four contests that Lewis sat out last season because of strained ligaments in one of his toes, the Ravens are 8-1 in nine games without Lewis.

The defense has recorded mixed results in Lewis' absence. Ranked 24th in average yards allowed prior to the win against the Cowboys, the unit is still 24th after Sunday's 16-13 overtime win against the San Diego Chargers.

Lewis attended the team's Nov. 9 practice, just two days prior to a home game against the Oakland Raiders. But he hasn't been seen much around the team's practice facility since then.

Lewis has been using a hyperbaric chamber to aid the healing process for the damaged triceps, and a source told Yahoo! Sports that Lewis has also been undergoing platelet-rich plasma therapy to return sooner.

Peter Allinson, a physician who specializes in hyperbaric medicine at MedStar Good Samaritan Hospital, said there are no studies that establish hyperbaric treatments as a clear method for healing sports injuries. But Allinson said there are an increasing number of anecdotal cases that suggest the treatment might work in sports medicine.

"Theoretically, it should speed healing. It definitely reduces the swelling of damaged tissue," he said of the treatment, which entails entering a pressure chamber that bolsters oxygen levels in the blood. Allinson said he has had success using the treatments to address everything from thermal burns to bone infections such as osteomyelitis.

"Athletic injuries fall more into the gray market for these kinds of treatments," he said. "As much as I would like to say this is a way to treat all sports injuries, I try to be very cautious and not advocate using something unless I know it has a good chance of working."

Allinson said he's also not familiar with any studies that show platelet-rich plasma therapy as a definitive means of treating sports injuries, though he said platelets do promote healthy tissue growth and have been effective in healing wounds.

Lewis' potential comeback would follow outside linebacker Terrell Suggs' return from a partially torn right Achilles tendon suffered in April. Suggs, the reigning NFL Defensive Player of the Year, played against the Texans and has been steadily increasing his workload with each game.

Harbaugh downplayed the notion of medical miracles, opting instead to give credit to Lewis and Suggs for rehabilitating their injuries as quickly and as effectively as they could.

"I just have so much confidence in who Ray is as a person and as a man," Harbaugh said. "And it's the same thing for Suggs. The thing … is, these guys are physically genetic, special DNA-type guys. … And they work harder than anybody in this room physically, that's for sure. So give credit where credit is due, and we'll just see how Ray does. But I know one thing: he's working harder than any of us can imagine to try to get back and get healthy."

On Sunday, Suggs reiterated what he's said all along: that the team is trying to hold its own until "The General" returns.

"We've been hit with a lot of injuries this year, but [Lewis] keeps telling us to stay the course and that the mission hasn't changed," Suggs said. "So hold it down until he gets back, and that's what we're doing."

The Ravens announced Monday that they had activated wide receiver David Reed from the physically unable to perform list and placed safety Anthony Levine on season-ending injured reserve with a shoulder injury.